The long-term goals of this project are to study the control and nature of recombination at the am locus of Neurospora, as well as the control of the expression of Glutamate dehydrogenase, the product of this gene. Glutamate dehydrogenase, an enzyme which is central in nitrogen metabolism of all eucaryotes, is highly conserved. The enzyme from Neurospora shows considerable homology, particularly in the amino terminal half, with that from vertebrates. Recent evidence has suggested that Glutamate dehydrogenase defects in humans are associated with a variety of neurological disorders including spinocerebellar syndrome. The difficulty of carrying out a program of fine structure genetic dissection of the gene of the glutamate dehydrogenase in higher eucaryotes makes this project with a microbial eucaryote particularly significant. As part of this current proposal the following studies will be carried out: (1) Recombination controlling elements in the 5 prime non-coding DNA will be identified and characterized (2) Mutations in the 5 prime non-coding DNA that effect gene expression will be characterized (3) The possibility of a distal element in the 5 prime non-coding DNA that effects gene expression will be examined (4) The nature of transformants obtained with the cloned am+ gene in a variety of vectors, using an am deletion as a recipient will be determined (5) The nature of non-homologous integration of am+ DNA during transformation will be determined by cloning and DNA sequencing the joint structure (6) Genes that flank the am gene will be cloned using the technique of chromosome walking.